Method for reducing surface roughness in a welded seam of an imaging belt

ABSTRACT

A welded seam of an imaging belt comprises a surface roughness. To reduce the surface roughness, the welded seam is treated by compressing a portion of the belt comprising the welded seam and adjacent belt portions and, while compressing, heating the welded seam to a heating temperature near but less than the glass transition temperature of the imaging layer of the belt, then cooling the welded seam to a cooling temperature. The compressing continues while the heating and cooling steps are repeated until the surface roughness is determined to be satisfactory. The process then ceases.

FIELD OF THE INVENTION

This invention relates in general to imaging belts and, morespecifically, to a process for reducing surface roughness in a weldedseam of an imaging belt.

BACKGROUND OF THE INVENTION

Flexible imaging member belts in electrostatographic imaging system arewell known in the art. Typical flexible imaging member belt include, forexample, electrophotographic imaging member belts for photoreceptors forelectrophotographic imaging systems, ionographic imaging member belts orelectroreceptors for electrographic imaging systems, and intermediateimage transfer belts for transferring toner images used in anelectrophotographic or an electrographic imaging system. These belts areusually formed by cutting a rectangular sheet from a web containing atleast one layer of thermoplastic polymeric material, overlappingopposite ends of the sheet, and joining the overlapped ends together toform a welded seam. The seam extends from one edge of the belt to theopposite edge. Generally, these belts comprise at least a supportingsubstrate layer and at least one imaging layer comprising thermoplasticpolymeric matrix material. The “imaging layer” as employed herein isdefined as the charge transport layer of an electrophotographic imagingmember belt, the dielectric imaging layer of an ionographic imagingmember belt, and the transfer layer of an intermediate transfer belt.Thus, the thermoplastic polymeric matrix material in the imaging layeris located in the upper portion of a cross section of anelectrostatographic imaging member belt whereas the substrate layerbeing in the lower portion of the cross section of theelectrostatographic imaging member belt. In the event that the imagingmember exhibits upward curling, an anti-curl backing layer is coated tothe back side (opposite to the side of the imaging layer) of thesubstrate layer. Although the flexible electrostatographic imagingmember belts of interest include the mentioned types, for simplicityreasons, the discussion hereinafter will be focused on theelectrophotographic imaging member belts as the representation.

Flexible electrophotographic imaging member belts are usuallymultilayered photoreceptors that comprise a substrate, an electricallyconductive layer, an optional hole blocking layer, an adhesive layer, acharge generating layer, and a charge transport layer and, in someembodiments, an anti-curl backing layer. One type of multilayeredphotoreceptor comprises a layer of finely divided particles of aphotoconductive inorganic compound dispersed in an electricallyinsulating organic resin binder. A typical layered photoreceptor havingseparate charge generating (photogenerating) and charge transport layersis described in U.S. Pat. No. 4,265,990, the disclosure of the foregoingpatent being hereby incorporated by reference verbatim, with the sameeffect as though such disclosure were fully and completely set forthherein. The charge generating layer is capable of photogenerating holesand injecting the photogenerated holes into the charge transport layer.

The flexible electrophotographic imaging member belts are fabricatedfrom a sheet cut from an imaging member web. The sheets are generallyrectangular or parallelogram in shape. All edges may be of the samelength or one pair of parallel edges may be longer than the other pairof parallel edges. The sheets are formed into a belt by joining theoverlapping opposite marginal end regions of the sheet. A seam istypically produced in the overlapping marginal end regions at the pointof joining. Joining may be effected by any suitable means. Typicaljoining techniques include welding (including ultrasonic), gluing,taping, pressure heat fusing, and the like. However, ultrasonic weldingis generally the chosen method for flexible imaging member seam joiningbecause it is rapid, clean (no solvents), produces a thin and narrowseam, and a low cost seaming technique. In addition, ultrasonic weldingis preferred because the mechanical pounding of the welding horn causesgeneration of heat at the contiguous overlapping end marginal regions ofthe sheet to maximize melting of one or more layers therein to form astrong seam joint. A typical ultrasonic welding process is carried outby holding down the overlapped ends of a flexible imaging member sheetwith vacuum against a flat anvil surface and guiding the flat end of anultrasonic vibrating horn transversely across the width of the sheet,over and along the length of the overlapped ends, to form a welded seam.

When ultrasonically welded into a belt, the seam of flexiblemultilayered electrophotographic imaging member belts may occasionallycontain undesirable high protrusions such as peaks, ridges, spikes, andmounds. These seam protrusion spots present problems during imagecycling of the belt in the machine because they interact with cleaningblades to cause blade wear and tear which ultimately affect cleaningblade efficiency and service life. Moreover, the protrusion high spotsin the seam may also interfere with the operation of subsystems ofcopiers, printers and duplicators by damaging electrode wires used indevelopment subsystems that position the wires parallel to and closelyspaced from the outer imaging surface of belt photoreceptors. Theseclosely spaced wires are employed to facilitate the formation of a tonerpowder cloud at a development zone adjacent to a tonor donor roll andthe imaging surface of the belt imaging member.

Since there is no effective way to prevent the generation of localizedhigh protrusions at the seam, imaging member belts are inspected, rightafter seam welding belt production process, manually by hand wearing acotton glove through passing the index finger over the entire seamlength and belts found catching the glove by the protrusions areidentified as production rejects. Both the time consuming procedure ofmanual inspection and the number of seamed belts rejected due to thepresence of high seam protrusions constitute a substantial financialburden on the production cost of imaging member belts.

Therefore, there is a need to provide seamed flexible imaging belts withan improved seam morphology which is free of protrusion spots tointeract against the machine operational subsystems. Furthermore, thesuccessful preparation of flexible imaging member belts having improvedseam morphology without protrusion spots can also eliminate the cleaningblade's nicking problem as well as enhance the blade's cleaningefficiency and extends its functional life. Very importantly, from theimaging member belt production point of view, that effective cutting ofunit manufacturing cost of seamed imaging belts can be achieved if aninnovative post seaming treatment process can be developed to remove theundesirable protrusion spots, provide a smoother seam surfacemorphology, and good mechanical seam strength.

Some prior art references are now discussed. U.S. Pat. No. 5,552,005 toMammino et al., issued Sep. 3, 1996, discloses a flexible imaging sheetand a method of constructing a flexible imaging sheet. The method ofconstructing a flexible imaging sheet comprises a step of overlapping, astep of joining, and a step of shaping. In the step of overlapping, afirst marginal end region and a second marginal end region of a sheetare overlapped to form an overlap region and a non-overlap region. Inthe step of joining, the first marginal end region and the secondmarginal end region of the sheet are joined to one another by a seam inthe overlap region. In the step of shaping, the overlap region is shapedto form a generally planar surface co-planar with a surface of thenon-overlap region. The flexible imaging sheet comprises a firstmarginal end region and a second marginal end region. The first marginalend region and the second marginal end region are secured by a seam toone another in the overlap region. The first marginal end region and thesecond marginal end region are substantially co-planar to minimizestress on the flexible imaging sheet. Minimization of stressconcentration, resulting from dynamic bending of the flexible imagingsheet during cycling over a roller within an electrophotographic imagingapparatus, is particularly accomplished in the present invention.

U.S. Pat. No. 4,883,742 to Walibillich et al., issued Nov. 28, 1989,discloses a process for seamless and firm joining of the end and/orlateral areas of thermoplastically processible photosensitive layers, bywhich the end and/or lateral areas of one or more solvent-free andunsupported thermoplastically processible photosensitive layers areoverlapped avoiding bubbles and with displacement of the air between theend and/or lateral areas, the total layer material is then heated underpressure and with joining of the overlapping end and/or lateral areas,and the resulting continuously joined photosensitive layer is then aftertreated and smoothed with shaping to exact size.

The disclosures of the foregoing U.S. patents to Mammino and Wallbillichare hereby incorporated by reference verbatim, with the same effect asthough such disclosures were fully and completely set forth herein.

While the above references disclose a variety of approaches forimproving the seam of flexible imaging member belts, these disclosedapproaches are either insufficient to meet the expectation, or oftentime introduce new set of undesirable outcomes such as seam vicinityimaging member wrinkling and belt circumferential dimension shrinkage.

Therefore, there is a need for developing a method for fabricating aflexible imaging member belt having an improved ultrasonically weldedseam free of protrusion spots, with a smoother surface morphology, andfree of spikes that are likely to damage the imaging machine subsystems.

SUMMARY OF THE INVENTION

In one aspect of the invention, there is provided a method for reducingsurface roughness in a welded seam of an imaging belt, the imaging beltcomprising first and second ends, the first and second ends overlappingand thereat joined by a welded seam, the welded seam comprising asurface roughness, the belt comprising an imaging layer, a glasstransition temperature corresponding to the imaging layer, the processcomprising the steps of:

at a fixed pressure, compressing a belt portion comprising the weldedseam and belt end portions adjacent thereto and, while compressing:

heating the welded seam to a heating temperature near but less than theglass transition temperature;

then cooling the welded seam to a cooling temperature;

the compressing, heating and cooling reducing the surface roughness; and

then determining when the surface roughness is satisfactory.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a prior art imaging belt 10 with first 12 and second 14ends overlapping and joined by a welded seam 11, the welded seam 11including a surface roughness comprising a high protrusion spike 101.

FIG. 2 depicts the belt 10 and welded seam 11 arranged with compressingand heating element 201 and compressing element 202, the arrangementsuitable for demonstrating one embodiment of the present invention.

FIG. 3 depicts the belt 10 and welded seam 11 arranged with compressingand heating element 201 and compressing and heating element 302, thearrangement suitable for demonstrating a further embodiment of thepresent invention.

FIG. 4 is a flow diagram of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In brief, a process for reducing surface roughness in a welded seam ofan imaging belt is provided. In accordance with the present invention,the welded seam is treated by compressing a portion of the beltcomprising the welded seam and adjacent belt portions and, whilecompressing, heating the welded seam to a heating temperature near butless than the glass transition temperature of the imaging layer of thebelt, then cooling the welded seam to a cooling temperature. Thecompressing continues while the heating and cooling steps are repeateduntil the surface roughness is determined to be satisfactory. Theprocess then ceases.

As used herein, the words “process” and “method” have identical meaningsand may be used interchangeably.

Referring now to FIG. 1, there is shown a prior art electrophotographicimaging belt 10 with a first end 12 and a second end 14. The imagingbelt 10 is flexible, and includes an outer surface 32 and an innersurface 34. As shown, the first end 12 and the second end 14 overlap ina region 30, the ends 12 and 14 being joined in the region 30 by anultrasonic welding process, thus forming a welded seam 11. As shown, thewelded seam 11 includes an outer welded seam region 11A and an innerwelded seam region 11B. Also as shown, the welded seam 11 includes asurface roughness comprising, for example, at least one high protrusionspike 101.

In one embodiment of FIG. 1, the welded seam 11 is formed by means of anultrasonic welding process.

Still referring to FIG. 1, as depicted the belt 10 comprises an imaginglayer 16. Moreover, it will be understood by those skilled in the artthat the imaging layer 16 may be characterized by one or more physicalparameters including, for example, a corresponding glass transitiontemperature.

Referring now to FIG. 2, there is shown the belt 10 and welded seam 11of FIG. 1 arranged with a compressing and heating element 201 and acompressing element 202. As will be discussed more fully in connectionwith FIG. 4 below, the arrangement of FIG. 2 is suitable fordemonstrating one embodiment of the present invention.

Referring now to FIG. 3, there is shown the belt 10 and welded seam 11of FIG. 1 arranged with a first compressing and heating element 201 anda second compressing and heating element 302. It will be understood thatthe element 201 of FIG. 3 is identical to the element 201 of FIG. 2. Aswill be discussed more fully in connection with FIG. 4 below, thearrangement of FIG. 3 is suitable for demonstrating a further embodimentof the present invention.

Referring now to FIG. 4, there is shown one embodiment of a flow diagramof the present invention. By means of this process, the surfaceroughness of the welded seam 11 is reduced in accordance with the methodcomprising steps 401-407 depicted in FIG. 4.

After starting, step 401, the process goes to step 407.

In step 407, at a controlled pressure, a belt portion comprising thewelded seam 11 and belt end portions adjacent thereto are compressedtogether.

In one embodiment, the outer welded seam region 11A and the inner weldedseam region 11B are compressed together by the compressing and heatingelement 201 and the compressing element 202 as depicted in FIG. 2.

In another embodiment, the outer welded seam region 11A and the innerwelded seam region 11B are compressed together by the first compressingand heating element 201 and the second compressing and heating element302 as depicted in FIG. 3.

In one embodiment, the controlled pressure substantially between 40 and80 pounds per square inch.

While the compressing forces that were initially applied in step 407continues to be maintained, the process goes to step 409.

In step 409, the welded seam 11 is heated for a fixed heating timeperiod to a heating temperature near but less than the glass transitiontemperature of imaging layer 16. As explained below, this heating of thewelded seam 11 can be done in at least two ways.

In one embodiment, the welded seam 11 is heated by means of thecompressing and heating element 201 applying heat to outer welded seamregion 11A as depicted in FIG. 2.

In another embodiment, as depicted in FIG. 3, the welded seam 11 isheated by means of the first compressing and heating element 201applying heat to the outer welded seam region 11A and the secondcompressing and heating element 302 applying heat to the inner weldedseam region 11B.

By means of using the embodiment of FIG. 2 or the embodiment of FIG. 3,the welded seam 11 becomes heated.

In one embodiment, the heating temperature is substantially between 0.5and 15 degrees Celsius below the glass transition temperature.

After step 409, while the compressing forces initially applied in step407 continue to be maintained, the process goes to step 411.

In step 411, the welded seam 11 is cooled for a fixed cooling timeperiod to a cooling temperature. As explained below, this cooling of thewelded seam 11 can be done in at least two ways.

In one embodiment, the welded seam 11 is cooled by the means of thecompressing and heating element 201 cooling the outer welded seam region11A as depicted in FIG. 2.

In another embodiment, as depicted in FIG. 3, the welded seam 11 iscooled by means of the first compressing and heating element 201 coolingthe outer welded seam region 11A and the second compressing and heatingelement 302 cooling the inner welded seam region 11B.

By means of using the embodiment of FIG. 2 or the embodiment of FIG. 3,the welded seam 11 becomes cooled.

In one embodiment, the cooling temperature is substantially roomtemperature.

In one embodiment, the cooling step 411 comprising a step of cooling thesingle heating element 201 of FIG. 2 or the two heating elements 201 and302 of FIG. 3 with a fluid. In one embodiment, the fluid compriseswater.

It will be appreciated that step 407's compressing, step 409's heatingand step's 411 cooling ultimately result in reducing the surfaceroughness of the welded seam 11. The foregoing reduction of welded seam11's surface roughness includes, without limitation, the elimination ofthe protrusion spike 101.

After step 411, while the compressing forces initially applied in step407 continue to be maintained, the process goes to step 413.

In step 413, it is determined when the surface roughness of the weldedseam 11, which surface roughness currently has been reduced as acumulative result of the step 407 compressing, step 409 heating and step411 cooling, is satisfactory.

In one embodiment, step 413 includes a step of determining when theprotrusion spike 101 of the welded seam 11 has been eliminated.

In another embodiment, step 413 includes a step of determining when thesurface roughness of the welded seam 11 has been reduced by anacceptable amount. For example, in one embodiment an acceptable amountof surface roughness reduction of the welded seam 11 comprises about 40%with respect to the original roughness of the welded seam 11.

In one embodiment, the determining step 413 comprises a step ofdetermining a total (cumulative) heating period during which the weldedseam 11 has been heated. For example, in one embodiment the determiningstep 413 determines when the heating step 409 has been performed a fixednumber of times.

When step 413 determines that the surface roughness of the welded seam11 is not satisfactory (corresponding to a step 413 NEGATIVE resultdepicted as the “NO” branch in FIG. 4), the process returns to step 409,whereupon the heating step 409, cooling step 41 1, and determining step413 are repeated.

Otherwise, when step 413 determines that the surface roughness of thewelded seam 11 is satisfactory (corresponding to a step 413 POSITIVEresult depicted as the “YES” branch in FIG. 4), the process goes to step415.

In step 415, the compressing initially begun in prior step 407 nowceases.

In one embodiment, the imaging belt 10 comprises a photoreceptor belt.

In a further embodiment, the imaging belt 10 comprises anelectroreceptor belt.

In a still further embodiment, the imaging belt 10 comprises anintermediate image transfer belt.

In summary, there is provided a method (depicted in FIG. 4) for reducingsurface roughness in a welded seam 11 of an imaging belt 10, the imagingbelt 10 comprising first 12 and second 14 ends, the first 12 and second14 ends overlapping and thereat joined by a welded seam 11 (comprisingouter welded seam region 11A and inner welded seam region 11B), thewelded seam 11 comprising a surface roughness including a protrusionspike 101, the belt 10 comprising an imaging layer 16, a glasstransition temperature corresponding to the imaging layer, the methodcomprising the steps of:

at a controlled pressure, compressing (step 407) a belt portioncomprising the welded seam 11 and belt end portions adjacent theretoand, while compressing:

heating (step 409) the welded seam 11 to a heating temperature near butless than the glass transition temperature;

then cooling (step 411) the welded seam 11 to a cooling temperature;

the compressing, heating and cooling reducing the surface roughness (aswell as eliminating the protrusion spike 101); and

then determining (step 413) when the surface roughness is satisfactory.

The method further comprises a step of repeating (corresponding to thenegative or “NO” result of determining step 413) the heating, coolingand determining steps (respectively steps numbered 409, 411 and 413)until the determining step (reference number 413) determines that thesurface roughness of the welded seam 11 is satisfactory.

Also, the method comprises a step (415) of ceasing (corresponding to thepositive or “YES” result of determining step 413) the compressing (whichwas begun in step 407) when the determining step (413) determines thatthe surface roughness of the welded seam 11 is satisfactory.

While various embodiments of a method for reducing surface roughness ina welded seam of an imaging belt, in accordance with the presentinvention, have been described hereinabove, the scope of the inventionis defined by the following claims.

What is claimed is:
 1. A method for reducing surface roughness in awelded seam of an imaging belt, the imaging belt comprising first andsecond ends, the first and second ends overlapping and thereat joined bya welded seam, the welded seam comprising a surface roughness, the beltcomprising an imaging layer, a glass transition temperaturecorresponding to the imaging layer, the method comprising the steps of:at a controlled pressure, compressing a belt portion comprising thewelded seam and belt end portions adjacent thereto and, whilecompressing: heating the welded seam to a heating temperature near butless than the glass transition temperature; then cooling the welded seamto a cooling temperature; the compressing, heating and cooling reducingthe surface roughness; and then determining when the surface roughnessis satisfactory.
 2. The method of claim 1, the surface roughnesscomprising a protrusion spike.
 3. The method of claim 1, the welded seamformed by means of an ultrasonic welding method.
 4. The method of claim1, the controlled pressure substantially between 40 and 80 pounds persquare inch.
 5. The method of claim 1, the heating temperaturesubstantially between 0.5 and 15 degrees Celsius below the glasstransition temperature.
 6. The method of claim 1, the coolingtemperature substantially at room temperature.
 7. The method of claim 2,further comprising a step of repeating the heating, cooling anddetermining steps until the determining step determines that the surfaceroughness is satisfactory.
 8. The method of claim 7, including a step ofdetermining when the protrusion spike has been eliminated.
 9. The methodof claim 7, including a step of determining when the surface roughnesshas been reduced by about 40% with respect to its original roughness.10. The method of claim 1, comprising a step of ceasing the compressingwhen the determining step determines that the surface roughness issatisfactory.
 11. The method of claim 1, the heating step performed fora fixed heating time period.
 12. The method of claim 11, the determiningstep comprising determining when the heating step has been performed afixed number of times.
 13. The method of claim 1, the imaging beltcomprising outer and inner surfaces, the heating step comprising a stepof applying heat to the outer surface.
 14. The method of claim 13, theheating step further comprising a step of applying heat to the innersurface.
 15. The method of claim 1, the heating step performed by meansof at least one heating element, the cooling step comprising a step ofcooling the at least one heating element with a fluid.
 16. The method ofclaim 15, the fluid comprising water.
 17. The method of claim 1, theimaging belt being flexible.
 18. The method of claim 17, the imagingbelt comprising a photoreceptor belt.
 19. The method of claim 17, theimaging belt comprising an electroreceptor belt.
 20. The method of claim17, the imaging belt comprising an intermediate image transfer belt.